Granting a User Permissions to Pass a Role to an AWS
Service

To configure many AWS services, you must pass an IAM
role to the service. This allows the service to later assume the role and perform
actions on
your behalf. You only have to pass the role to the service once during set-up, and
not every
time that the service assumes the role. For example, assume that you have an application
running
on an Amazon EC2 instance. That application requires temporary credentials for authentication,
and
permissions to authorize the application to perform actions in AWS. When you set up
the
application, you must pass a role to EC2 to use with the instance that provides those
credentials. You define the permissions for the applications running on the instance
by
attaching an IAM policy to the role. The application assumes the role every time it
needs to
perform the actions that are allowed by the role.

To pass a role (and its permissions) to an AWS service, a user must have permissions
to
pass the role to the service. This helps administrators ensure that only
approved users can configure a service with a role that grants permissions. To allow
a user to
pass a role to an AWS service, you must grant the PassRole permission to the
user's IAM user, role, or group.

When you create a service-linked role, you must also have permission to pass that
role to
the service. Some services automatically create a service-linked role in your account
when you
perform an action in that service. For example, Amazon EC2 Auto Scaling creates the
AWSServiceRoleForAutoScaling service-linked role for you the first time that you
create an Auto Scaling group. If you try to create an Auto Scaling group without the
PassRole permission, you receive an error. To learn which services support
service-linked roles, see AWS Services That Work with
IAM. To learn which services
automatically create a service-linked role when you perform an action in that service,
choose
the Yes link and view the service-linked role documentation for the
service.

A user can pass a role ARN as a parameter in any API operation that uses the role
to assign
permissions to the service. The service then checks whether that user has the
iam:PassRole permission. To limit the user to passing only approved roles, you
can filter the iam:PassRole permission with the Resources element of
the IAM policy statement.

Example 1

Imagine that you want to grant a user the ability to pass any of an approved set of
roles
to the Amazon EC2 service upon launching an instance. You need three elements:

An IAM permissions policy attached to the role that determines
what the role can do. Scope permissions to only the actions that the role must perform,
and
to only the resources that the role needs for those actions. You can use AWS managed
or
customer-created IAM permissions policy.

{
"Version": "2012-10-17",
"Statement": {
"Effect": "Allow",
"Action": [ "A list of the permissions the role is allowed to use" ],
"Resource": [ "A list of the resources the role is allowed to access" ]
}
}

A trust policy for the role that allows the service to assume the
role. For example, you could attach the following trust policy to the role with the
UpdateAssumeRolePolicy action. This trust policy allows Amazon EC2 to use the role
and the permissions attached to the role.

An IAM permissions policy attached to the IAM user that allows
the user to pass only those roles that are approved. iam:PassRole usually is
accompanied by iam:GetRole so that the user can get the details of the role to
be passed. In this example, the user can pass only roles that exist in the specified
account
with names that begin with EC2-roles-for-XYZ-:

Now the user can start an Amazon EC2 instance with an assigned role. Applications
running on the
instance can access temporary credentials for the role through the instance profile
metadata.
The permission policies attached to the role determine what the instance can do.

Example 2

Amazon Relational Database Service (Amazon RDS) supports a feature called Enhanced
Monitoring. This feature enables
Amazon RDS to monitor a database instance using an agent. It also allows Amazon RDS
to log metrics to
Amazon CloudWatch Logs. To enable this feature, you must create a service role to
give Amazon RDS permissions to
monitor and write metrics to your logs.

Choose the AWS Service role type, and then choose the
Amazon RDS Role for Enhanced Monitoring service. Then choose
Next: Permissions.

Choose the AmazonRDSEnhancedMonitoringRole, permissions policy and
then choose Next: Review.

For Role name, type a role name that helps you identify the purpose
of this role. Role names must be unique within your AWS account. They are not
distinguished by case. For example, you cannot create roles named both
PRODROLE and prodrole. Because various
entities might reference the role, you cannot edit the name of the role after it has
been
created.

(Optional) For Role description, type a description for the new
role.

Review the role and then choose Create role.

The role automatically gets a trust policy that grants the
monitoring.rds.amazonaws.com service permissions to assume the role. After it
does, Amazon RDS can perform all of the actions that the AmazonRDSEnhancedMonitoringRole
policy allows.

The user that you want to enable Enhanced Monitoring needs a policy that includes
a
statement that allows the user to pass the role, like the following. Use your account
number and
replace the role name with the name you provided in step 3:

You can combine this statement with statements in another policy or put it in its
own
policy. To instead specify that the user can pass any role that begins with RDS-,
you can replace the role name in the resource ARN with a wildcard, for example:

"Resource": "arn:aws:iam:::role/RDS-*"

Javascript is disabled or is unavailable in your browser.

To use the AWS Documentation, Javascript must be enabled. Please refer to your browser's
Help pages for instructions.